Bolden is leading international efforts to get humans on the planet, but when asked to find one word to describe the challenge, he said: "Hard. Mars is really, really hard."

He said space agencies were currently approaching the "walk" stage of their efforts, noting that more technological development as well as a greater understanding of the human body and "how it reacts" to the conditions of Mars.

Could a Brit reach the Red Planet in our lifetimes?

He added that testing would also have to take place on Earth's moon before astronauts could venture further toward their goal.

We need a proving ground, and that's our moon. So we will go back into lunar orbit with what we hope will be an asteroid or part of an asteroid, and develop some of the techniques.

– Charles Bolden, Nasa Administrator

Given the international nature of the space effort - India recently put its Mars mission into orbit while the European Space Agency has two expeditions planned - Bolden says he would not be surprised to see a British explorer walk on Mars at some point.

However, he also warned that the decision by previous British governments to withdraw from space exploration should not be repeated - saying space exploration can not be "put on the back burner" and resumed whenever interested.

Nonetheless, he has an optimistic vision: "The UK is a perfect partner to try to venture off into the far reaches of the solar system with."